[Paratesticular Low-Grade Fibromyxoid Sarcoma: A Case Report].

A 36-year-old man presented with painless swelling in the right side scrotum. Ultrasonography showed a hypoechoic tumor with mosaic pattern. Plain computed tomograghy (CT) revealed a 67 mm scrotal cystic lesion with low density area. We suspected an intrascrotal tumor and performed right side radical orchiectomy. The removed sample was yellow clear and elastic hard. A 7 cm multilocular cystic tumor was present on the head side of the normal testis. The cut-surface and the contents of the mass revealed a jelly-like viscous liquid. On the microscopic examination, the tumor was composed of mucinous stroma and spindle-shaped atypical cells with hyperchromatic oval nuclei and eosinophilic cytoplasm. There was a characteristic network of blood vessesls with hyperhyalinization in the myxoid zones. Immunohistochemically, CDK4, MDM2, AE1/AE3, S-100, Alpha-SMA and desmin were negative, but MUC4 showed focal cytoplasmic positivity in the neoplastic cells. In the reverse transcription polymerase chain reaction assay, no FUS-CREB3L2/FUS-CREB3L1 fusion transcripts were identified although the detectable messages of the housekeeping genes were noted. The tumour was finally diagnosed as a paratesticular low-grade fibromyxoid sarcoma. Postoperative course was uneventful and no recurrence or metastasis was seen four months after the operation.